1. Field of the Invention
The present invention relates to FGF-1 and mutants of FGF-1 affecting the signaling of cellular growth, differentiation, and angiogenesis.
2. References
Various publications are referred to in parentheses throughout this application. Each of these publications is incorporated by reference herein. Complete citations of scientific publications are set forth below, or in the text of the specification.    Assoian, R. K. (1997) Anchorage-dependent cell cycle progression. J Cell Biol, 136, 1-4.    Belford, D. A., Hendry, I. A. and Parish, C. R. (1992) Ability of different chemically modified heparins to potentiate the biological activity of heparin-binding growth factor 1: lack of correlation with growth factor binding. Biochemistry, 31, 6498-6503.    Brooks, P., Clark, R. and Cheresh, D. (1994a) Requirement of vascular integrin alpha v beta 3 for angiogenesis. Science, 264, 569-571.    Brooks, P., Montgomery, A., Rosenfeld, M., Reisfeld, R., Hu, T., Klier, G. and Cheresh, D. (1994b) Integrin alpha v beta 3 antagonists promote tumor regression by inducing apoptosis of angiogenic blood vessels. Cell, 79, 1157-1164.    Brooks, P. 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3. Description of Related Art
Fibroblast growth factors (FGFs) constitute a family of heparin-binding polypeptides involved in the regulation of biological responses such as growth, differentiation, and angiogenesis. They are also implicated in inflammation, excess wound healing, and resistance of tumor cells to chemotherapeutic agents (chemoresistance).
The FGF family currently consists of 24 members, with FGF-1 (acidic FGF) and FGF-2 (basic FGF) the most extensively studied. The biological effects of FGFs are mediated by four structurally related receptor tyrosine kinases, denoted FGFR1, FGFR2, FGFR3, and FGFR4. The binding of FGF to its receptor results in receptor dimerization and subsequent autophosphorylation on specific tyrosine residues within the intracellular domain (Klint and Claesson-Welsh, 1999; Powers et al., 2000; Presta et al., 2005; Ullrich and Schlessinger, 1990)
Integrins are a family of cell adhesion receptors that recognize extracellular matrix ligands and cell surface ligands (Hynes, 2002). Integrins are transmembrane α-β heterodimers, and at least 18 α and β subunits are known (Shimaoka and Springer, 2003). Integrins transduce signals to the cell upon ligand binding, and their functions are in turn regulated by the signals from within the cell (Hynes, 2002). Ligation of integrins triggers a large variety of signal transduction events that serve to modulate cell behavior including proliferation, survival/apoptosis, shape, polarity, motility, gene expression, and differentiation. Integrin-stimulated pathways are very similar to those triggered by growth factor receptors and are intimately coupled with them. It has been proposed that many cellular responses to soluble growth factors, such as epidermal growth factor, platelet-derived growth factor, and thrombin, are dependent upon the cell's adherence to extracellular matrix ligands via integrins. Integrins lie at the basis of such anchorage-dependent cell survival and proliferation (Assoian, 1997; Frisch and Screaton, 2001; Schwartz and Assoian, 2001).
It has been proposed that FGF-2-induced angiogenesis requires integrin signaling from the extracellular matrix (crosstalk between integrins and FGF receptors). Indeed antibody against integrin αvβ3 blocks FGF-2-induced angiogenesis (Brooks et al., 1994a; Brooks et al., 1994b). It has been reported that FGF-2 enhances αvβ3 expression during angiogenesis (Brooks et al., 1994a). Antibody or cyclic peptide antagonist of αvβ3 inhibits this αvβ3 upregulation (Brooks et al., 1994a; Brooks et al., 1995; Friedlander et al., 1995). It has been shown that integrin and growth factors are colocalized under certain condition. For example coimmunoprecipitation studies revealed direct biochemical interaction between αvβ3 and FGFR1 in the presence of both FGF-2 and fibrinogen (Sahni and Francis, 2004). These findings suggest integrin and FGFR are colocalized on the membrane in the presence of FGF-2. It has not been established how integrins and FGFR crosstalk in FGF-2 signaling.
It has been reported that substrate-bound FGF-2 promotes endothelial cell adhesion by interacting with integrin αvβ3 (Rusnati et al., 1997) and induces endothelial cell proliferation, motility, and the recruitment of FGFR1 in cell substrate contact (Tanghetti et al., 2002). Anti-αvβ3 antibodies block cell proliferation on immobilized FGF-2, but deletion of the tyrosine kinase portion of FGFR blocks cell proliferation induced by immobilized FGF-2. Thus it has been proposed that αvβ3 is required but not sufficient to transduce mitogenic signals of FGF-2 (Tanghetti et al., 2002). It is unclear how integrins interact with FGF-2 or whether this interaction is biologically relevant since heat-denatured FGF-2 still supports integrin binding (Tanghetti et al., 2002).